There has been one called-out people of God from Adam through the end of this present age.
First, the term ekklesia according to its etymological meaning cannot be found in the history of the Greek language where it is was ever used to simply mean "called out of the world." A term is defined by context and by usage and "called out of the world" is a nexistent usage in Greek literature and the Greek Septuigent or the Greek New Testament. So you are simply being imaginative but rather than exegetical.
Furthermore, you are confusing the effectual call (regeneration) with the church.
Old Testament saints may not have had firsthand knowledge of the Christ, but their faith was in Him nonetheless. The elect of God, regardless of when, have been predestined from all eternity. Their salvation was wrought in Christ; even those who died prior to Christ's advent:
Ephesians 1:4 just as He chose us in Him before the foundation of the world, that we would be holy and blameless before Him [emphasis mine].
Did the Father choose only those who would be in the New Testament Church, or did He choose all who He intended to be holy and blameless before Him (in Christ)? It's a rhetorical question, with the answer obviously being the latter proposition.
Now you are confusing election "in Christ" with the church. No place in Scripture does it say the church existed before the world began - nowhere.
Only by confusing regeneration and election with the church can you invent your doctrine.
Again, the founder, the foundation, the first members added to the church HAD NLD TESTAMENT EXISTENCE - NONE - NOTHING - NADA! Paul tells you that the New Testament church is a New Testament truth/revelation not an Old Testament truth/revelation.
Your whole position is a position of inferences based upon confusing terms, confusing doctrines.
The visible church is simply a way of explaining of what the eye can see in regards to the physical construction of the local church.
If that is so, then why does God forbid to have some kind of "brethren" in the congregational body of water baptized believers what your doctrine of the church includes??? Those "brethren" who act immoral or go into false doctrine are to be removed from the Lord's churches (1 Cor. 5:11; 2 Thes. 3:6 "brother") but your kind of invented church necessarily must include them????
You are doing the same thing that Augustine and Luther did with the parable of the tares in Matthew 13. Matthew 13 is the text where the universal visible and universal invisible church was hatched. The field is "the world" not the church. The tares and seed are the professing "kingdom" not the church. Prior to 400 A.D. the "universal" church cannot be found in Christian literature. Indeed, the early church fathers called each local congregation "catholic" simply to contrast it with the Jewish synoguoge which was required you to be Jewish. The New Testament congregation was "universal" in the make up of its membership requiring no specific ethnicity.This is why those that are truly saved are member of the invisible church; the church that cannot be seen with eyes, but that is known by God.
Prior to the Reformation, you cannot find cannot find any "universal invisible church" in Christian literature. You can find the prospective future church made up of all the elect, but which is an actual future assembly in one place, thus continuing the historic usage of the term ekklesia as a visible localized body of baptized believers, except in this case, its location is in heaven and yet future WITHOUT ANY PRESENT EXISTENCE.